Mechanism for limiting runaway speed of adjustable blade turbines



Feb. 25, 1958 VQADEN 2,824,716

MECHANISM FOR LIMITING RUNAWAY SPEED OF ADJUSTABLE BLADE TURBINES FiledDec. 27. 1952 7 Sheets-Sheet 1 To .Sl/MP Fear! J KE-$50k! wees IN VENTORGRANT hf l oxwz/v Feb. 25, 1958 G. H. VOADEN MECHANISM FOR LIMITINGRUNAWAY SPEED OF ADJUSTABLE BLADE TURBINES Filed Dec. 27. 1952 '7Sheets-Sheet 2 INVENTOR G/eAA/TH. VOADEN ATTORNEY Feb. 25, 1958 G. H.VOADEN 2,824,716

MECHANISM FOR LIMITING RUNAWAY SPEED OF ADJUSTABLE BLADE TURBINES FiledDec. 27. 1952 7 Sheets-Sheet 3 N \9 INVENTOR.\

GRANT h. Vanna/v BY ATTORNEY Feb. 25, 1958 G. H. VOADEN 2,824,716

MECHANISM FOR LIMITING RUNAWAY SPEED OF ADJUSTABLE BLADE TURBINES FlledDec. 27, 1952 7 Sheets-Sheet 4 M 2 92 I y YIIIIIIIA'E'IIIIl/Ili 15 /74 7175 j 173 so Z I FROM PRESEIIRE $0|IRC Fig.6

78 INVENTOR.

GRANT h. Vonzuw Feb. 25, 1958 Filed Dec. 27. 1952 VII/Ill G. H. VOADMECHANISM FOR LIMITING RUNAWAY SPEED OF ADJUSTABLE BLADE TURBINES 'rSheets-Sheet 5 l l l T r-#72 INVENTOR. 62/ h. VOADEN BY I ATTORNEY Feb.25, 1958 a. H. VOADEN 2,324,716

uscmmxsu FOR LIMITING RUNAWAY SPEED OF I ADJUSTABLE BLADE TURBINES FiledDec. 27. 1952 7 Sheets-Sheet 6 .11 m o a.

GR llJ anpav I BY Feb. 25, 1958 G. H. VOADEN 2,824,716

MECHANISM FOR LIMITING RUNAWAY SPEED OF ADJUSTABLE BLADE TURBINEJS FiledDec. 27. 1952 7 Sheets-Sheet 7 8 INVENTOR.

' GRANT Vanna/v BYXW ATTORN Y United States Patent C MECHANISM FORLIMITING RUNAWAY SPEED OF ADJUSTABLE BLADE TURBINES Grant H. Voaden,York, Pa., assignor to S. Morgan Smith Company, York, Pa., a corporationof Pennsylvania Application December 27, 1952, Serial No. 328,161

14 Claims. (Cl. 253-143) This invention relates to an addition to thenormal control mechanism of a Kaplan type turbine, said additioncomprising positive means for limiting the runaway speed which occurs ifsaid normal control mechanism should fail to function as intended. Moreparticularly, the invention relates to a hydraulic turbine having aKaplan type runner or propeller on which the blades are movable fordisposing the same at various pitches, thereby to obtain the optimumefliciency of the turbine over its entire range of operation.

Adjustable blade runners or propellers have been utilized in hydraulicturbines for a number of years past in hydroelectric power plantinstallations for purposes of driving electric generators. In suchinstallations, the head of water impounded by a dam will vary duringdifferent times of the year and especially between high water or floodstages which usually occur in the spring months and the low water stageswhich occur during the dry summer months. Also, load requirements varyon generators in such hydroelectric power plants during and between peakperiods and off-peak periods occurring each day.

The adjustable blade type Kaplan turbine is admirably suited to meetthese various changing conditions in hydroelectric power plants. Waterfor driving the turbine runner is usually introduced into the runnercavity by an annular arrangement of a plurality of angularly adjustablewicket gates. These gates are adjusted to vary the quantity of watersupplied to the runner. In the space between the gates and the runner,the water whirls inward and downward, the whirl component being greatestat low gate openings and decreasing as the gates are opened and thequantity of water increased. It is discharged from the runner in asubstantially axial direction. When the Wicket gatesare adjusted, forexample, to meet changing load-demands, the blade pitch of the turbinealso is adjusted automatically and substantially simultaneously with thegate movement so that at all gate positions the related blade angle issuch as to produce maximum turbine efliciency. As the gates open, theblades normally are moved to steeper angles and vice versa.

The turbine runner blades are pivotally supported by a hub from whichthe blades project uniformly, the hub having bearings which pivotallyreceive-trunnions projecting inwardly from the blades. These blades canbe varied in pitch, simultaneously, between predetermined optimum openand closed, or respectively steep and flat, positions within requiredlimits by the use of a hydraulic cylinder or a geared motor usuallycontained in the turbine shaft. The pitch of the blades may be varied ineither direction through a'predetermined range, usually, but withoutrestriction thereto, about 26, as dictated by a governor embodied in thenormal control system for each turbine.

If the hydroelectric unit, while operating under load at normal speedis, for example, suddenly disconnected from its load, such as by theopening of the switch congetting the generator outgoing terminals to thepower 2,824,716 Patented Feb. 25, 1958 transmission line, the governorand control system normally function to move the wicket gates to closedpositions, thus shutting off the water supply so as to stop the unit.The blades of the turbine runner also simultaneously will be moved toclosed position. However, if these devices do not function normally andrelatively quickly, so-called runaway speed will be developed by theturbine and the generator driven thereby. In turbines of the typedescribed, maximum runaway speeds normally amount to at least two andone-half times the normal speed of the turbine. Obviously it isnecessary to design generators to withstand such maximum contemplatedrunaway speeds.

It is sometimes impracticable and always expensive to design a generatorcapable of sustaining runaway speeds of the magnitude of two andone-half or more times the normal speed. Considering the fact thatgenerators in many relatively large hydroelectric power installationscos-t upward from $1,000,000, even any small percentagewise increase incost amounts to a sizable sum. Further, the cost of a given generatorincreases at an accelerating rate as the runaway speed for which it mustbe designed increases. In addition, while there have been relatively fewfailures of the normal control mechanism resulting in serious damage tohydroelectric units, nevertheless both the generator and the turbine fordriving the same must be designed with adequate factors of safety toenable the same to withstand runaway speeds of the maximum magnitude asdescribed above. So designing and building the turbines and generatorsadds very materially to the costs thereof as compared with the cost ofthe same if such maximum runaway speeds could be minimized by the use ofone or more of the devices described and claimed herein.

The individual blades of the runner customarily have their axes ofpitching so located that at the normal or rated rotational speed of theunit, the maximum external force required to increase pitch approximatesthe maximum force required to decrease pitch.

As the speed of the turbine increases above the rated speed when runawayspeed occurs, the net result of the change in the forces tending to openthe blades becomes progressively and substantially greater. The effectof this tendency can be calculated from the design of the runner and/ordetermined by laboratory testing of a working model.

ing axes of the blades relative to the blade areas. It is essential forthe proper functioning of certain of the vari ous devices covered bythis invention that the pivot axes of the blades are so located relativeto the blade areas that at any rotational speed above rated speed, theblades have a positive, inherent tendency to increase pitch, i. e. to goopen, regardless of their pitch or angular positions. It will be assumedregarding said certain devices, except where specifically statedotherwise, that the blade pitching axes are located to produce thisopening tendency at all speeds above rated speed.

A characteristic of one form of adjustable blade turbine, to which thisinvention applies, is that at a given head, if the turbine is free torotate at will Without load, the runaway speed is lower at the maximumpermit-ted open blade pitch than at lower pitches within the norm-a1pitching range. This is so because the component of forcein thedirection of rotation of the turbine is reduced as the blades open; forexample if the blade position were axial with the turbine shaft, thevrotational component of the force is approximately zero. Thischaracteristic is used advantageously in conjunction with various formsof runaway speed control means comprising the present invention.

It is the principal and basic object of the present Any desired neteffect of this inherent tendency can be obtained by proper location ofthe pitch- 1 vention to provide various forms of control means by whichthe runaway speed of. an adjustable blade turbine may be positivelylimited to an amount above normal, or rated speed, for which it iseconomically and practically feasible to design and constructthe.generator whilemaintaining the usual factors of safety against damage bysaid runaway speed.

It is another object of the invention to provide in adjustable bladeturbines various selective embodiments of control means respectivelyoperable to hold the unit speeds of said turbines within predeterminedlimits when the normal control means, such as the governing equipment orpressure system, fails to function in its customary manner.

It is. still. another. object of the invention to provide, in.adjustable blade turbines having blades which inherently tend to move tothe open or steep positions thereof at rotational. speeds in excess ofrated speed, control means which utilize. such tendency to operate orfunction to hold. theunit speeds of said turbines within. predeterminedlimits when the normal control means fail to function as contemplated.

It is another object of the invention to embody actuating means withinthe control mechanisms referred to above, said actuating means beingoperable upon the occurrence. of overspeed of a predetermined maximum tofree the blades from. the control of the normal positioning means. andpermit movement of the blades toward the normal maximum permitted openpositions thereof, or beyond said normal maximum open positions, therebyto restrict the speed of the turbine to a value corresponding to that ofthe open position of the blades to which they have been moved by saidhydraulic unbalance.

It is still another object of. the invention to utilize respectively invarious forms of the abovementioned control devices fluid pressures and/or centrifugal forces in excess of predetermined, normal amounts forpurposes of actuating the control means to effect movement of the bladestoward the maximum permitted open positions thereof so as to maintainthe speed of the turbine within safe limits when conditions occurtending to produce runaway speeds.

One further object of the invention is to utilize respectively in theaforementioned various embodiments of control mechanisms, hydraulic,electrical and mechanical means to control and effect movement of theblades to ward the open positions thereof so as to limit the speed ofthe turbine when conditions occur tending to produce runaway speeds.

A still further object of the invention is to provide a number ofembodiments of control and actuating means for the blades of anadjustableblade turbine operable to prevent the occurrence of unsafespeeds in excess of normal, said control means being rugged, durable,and positive, capable of ready manipulation, certainty of functioning,easily adjusted, relatively inexpensive to manufacture and install,capable of long use with minimum service requirements, and readilyadapted for installation not only in newly manufactured turbines butalso to being installed in existing turbines in the field.

Details of the foregoing objects and of the invention, as well as otherobjects thereof, are set forth in the following specification andillustrated in the accompanying drawings forming a part thereof.

In the drawings:

Fig. 1 is a vertical elevation, partly in section and partlydiagrammatic, of an exemplary-installation of a hydroelectric unitincluding a turbine having adjustable blades .for purposes ofaccommodatingvariations of power requirements from various electricalappliances external to the hydroelectric unit andyet. maintain theoptimum efiiciency of. the hydroelectric unit over'the operating range.This unit also includes one embodiment of control means which limitsthe.maximum runaway speed of the unit to a predetermined maximum for whichthe unit has been designed.

(iii

Fig. 2 is a fragmentary sectional view on a considerably enlarged scalecompared to Fig. 1 showing certain details of the embodiment of controlmeans arranged to maintain the blades against movement except asrequired during normal operation under the control of the governor.

Fig. 3 is a sectional view similar to Fig. 2 but illustrating onlyone-half of the mechanism shown therein, said view showing the controlmechanism in the position the parts would assume, due to centrifugalforce, were the normal speed control mechanism such as the gov ernor andpressure system to fail and thereby permit the unit to reach apredetermined overspeed at which movement of the blades toward openposition should be permitted.

Fig. 4 is a still further enlarged sectional fragmentary view of afurther embodiment of blade control mechanism utilizing hydraulicprinciples and operable to permit movement of the blades toward openposition upon a predetermined overspeed condition occurring, saidcondition being evidenced in the normal blade servomotor.

by an increase in pressure under thepiston thereof above a predeterminedmaximum. In this view, the control means. is in a position to maintainthe blades against movement except as controlled normally by thegovernor.

Fig. 5 is a view similar to Fig.4 except that the control means ispositioned to permit relieving of the excess of fluid pressure on theunder side of the servomotor piston.

Fig. 6 is a diagrammatic and partially fragmentary as well as partlysectional view illustrating still another embodiment of blade controlmechanism responsive directly to rotational speed of the turbine andgenerator and upon said speed exceeding a predetermined amount in theevent of failure of the normal control mechanism, said control mechanismfunctions to permit the blades of the turbine to move toward openposition and thereby reduce the speed of the turbine. This embodimentalso utilizes electrical means. In this view, the control mechanism ispositioned to maintain the blades of the turbine against movement exceptas controlled by the functioning of the normal control mechanism.

Fig. 7 is a view similar to Fig. 6 but showing the control mechanismpositioned to effect movement of the blades toward open position thereofin response to runaway speed conditions in excess of a predeterminedamount.

Fig. 8 is a partly sectional view of. an embodiment of control.mechanism. similar to that shown in Figs. 6 and 7 but including aslightly difierenttype of actuating mechanism.

Fig. 9 is an enlarged sectional view illustrating still anotherembodiment of blade control means utilizing hydraulically operated meanssimilarly to the embodiment in Figs. 4 and 5 but positioned differentlyin the unit for greater convenience under certain circumstances. In thisfigure, an oil head such as illustrated in the upper portion of Fig. 1is shown, said oil head embodying a fluid pressure relief valve arrangedto open automatically when pressures against the under surface of theservomotor piston exceed a predetermined. figure as a result of thespeed of the turbine exceeding a desired value. In this view the valveis shown in closed position such as when the unit is normally controlledby the'governor.

Fig. 10 is a fragmentary vertical-elevation partly broken. away andpartly in section, illustrating the details of still another embodimentof mechanically operable control mechanism responsive to runaway speedconditions of predetermined amount and-operable, due. to the tendency ofthe blades to move toward or to the. maximum permitted open positionupon the occurrence of such conditions, to yield to said tendency ofsaid blades to move:so. as to permit opening of the blades and effectreduction in the speed of the turbine.

Fig. 11 is a view somewhat similar to Fig. 10 but illus trating asimilar type of control mechanism usable in cons a junction with one ofthe other embodimentsof control mechanism illustrated hereinabove tosupplement the effectiveness thereof.

Description of adjustable blade turbine with normal controls In additionto serving the purpose of illustrating one embodiment of the invention,Fig. 1 will first be used as a basis for description of the normalconstruction and operation of an adjustable blade turbine and theconventional controls therefor. In the exemplary installation shown insaid figure, six main elements of such a unit are illustrated. Thesecomprise a diagrammatically illustrated electric generator 10, a turbinerunner 12 of the adjustable blade propeller type which depends from thegenerator and is rotatably supported to drive the generator, a bladecontrol valve 14, an oil head 16 which surmounts the generator 10, aservomotor 18, and blade actuating mechanism 2% In this illustration,which is intended solely by way of example, a servomotor 18 has beenselected as the means for varying the pitch of the blades 22 of therunner 12 as well as maintaining said blades in any desired operativeposition between substantially closed position and predetermined,desired, optimum open position in which the blades are at a considerableangle to the closed positions thereof. In Fig. 1 the blades are shown inapproximately their mid-travel position in accordance with theparticular design and arrangement of runner 12 shown herein. Though thisinvention is not restricted thereto, the blades move through an angle ofapproximately 26 in moving between the fullest permitted open positionand the closed position thereof.

While not illustrated herein, it will be understood by those familiarwith the art that surrounding the runner at a diameter slightly greaterthan that of the runner blades is a partly spherical, metal housing ordischarge ring to contain or restrict the water passing axially throughthe runner and that the water flow to the runner is controlled by aseries of wicket gates each movable about its own axis, but in unison,said axes being uniformly arranged around the axis of rotation of theturbine and said gates being movable between fully closed and fullyopened positions for purposes of varying the amount of water directedagainst the blades of the runner 12, thereby controlling the force whichdrives the runner 12 and thereby revolves the rotor of the generator 10.

The opening of the wicket gates is varied according to the load demandon the generator 10 through the medium of a governor systeminterconnected with said generator. Such governor is not illustrated inthe present drawings but it is believed that anyone skilled in this artis readily familiar with the type of governor referred to. When thewicket gates are adjusted to meet changing load demands on the generator10, the pitch of the blades 22 of the runner 12 is adjustedautomatically and substantially simultaneously with the gate movement sothat at all gate positions, the related blade angle is such as toproduce the maximum turbine efllciency. Thus, for example, as the gatesopen, the blades are pitched toward their maximum open position ofsteepest angles. Conversely, as the gates move toward closed position,the blades are correspondingly automatically pitched toward their flator closed position.

When it is desired, by way of further example, to shut down the unit,the wicket gates are closed and the runner blades are movedcorrespondingly to fully closed position in which the terminal endportions of the blades herein illustrated are disposed substantiallywithin a common plane in the preferred embodiment of the inventionalthough the hub ends of the blades are at an angle to the terminalends. It will be understood also that the generator 10 and the turbinemechanism for operating the same are supported byrustomary means withinhydroelectric power plants and the runner 12 is supported for rotationwithin the conventional turbine pit, such supporting structure not beingillustrated however.

The actuation of the blades 12 is accomplished, and said blades are alsomaintained in a desired setting, by positioning means comprising anexemplary blade servomotor 18 which has incorporated therein oneembodiment of the present invention. Control and actuation of the blades22 are achieved through the blade actuating mechanism 20 comprising partof said positioning means. By referring particularly to Fig. 1, it willbe seen that each blade 22 has a trunnion 24 rotatably supported withina bearing 26 extending into the hub 28 of the runner 12. Projectingtransversely to the inner end of each trunnion 24 and fixed thereto is arocker arm 30. Vertically movable within the hub is an operating rod 32which extends upwardly through the hub 28 and main shaft 34 to theservomotor piston 33. The main shaft 34 is attached to the upper end ofthe hub and to the blade servomotor housing 36 as clearly shown inFig. 1. The upper end of the operating rod 32 is directly connected topressure responsive means comprising the blade servomotor piston 33 ofthe blade servomotor 18.

Connected to the lower end of operating rod 32 is a crosshead 40, saidcrosshead having a plurality of arms corresponding to the number ofblades 22. A link bolt 42 is fixed to each of the arms of the crosshead40 as clearly shown in Fig. 1. A suitable link 44, such as a pair ofplates, pivotally interconnects the ends of each rocker arm 30 with alink bolt 42 on crosshead 40. Thus, as the piston 38 moves downward, theblades 22 will be rotated on the trunnion axes by the above describedmechanism in blade opening direction. Conversely, as the piston 38 ismoved upward, the blades 22 will be rotated on the trunnion axes towardclosed position or clockwise as viewed in Fig. 1. A generator shaft 46is connected to the upper end of the blade servomotor casing 36 and theupper end of said shaft 46 is connected to the rotor, not shown, of thegenerator 10 so as to drive the same when the runner 12 is rotated.

Surmounting the generator 10 is an oil head 16 referred to hereinabove,the same comprising a casing 48 which is stationarily fixed to the frameof the generator 10. Supported on the inside of the casing 48 and fixedthereto are two separate hydraulic fluid compartments 50 and 52. Ingeneral, but without restriction thereto, it will be understood hereinthat oil is the prepacking box 56 prevents the escape of fluid throughthe i bearing between the compartment 50 and the tube 5'4 but the upperend of the tube 54 is provided with a plurality of fluid ports 58through which fluid may pass from the compartment 50 to tube 54 and intoa small confining housing 60 connected between the lower end of inneroil tube 54 and the upper surface of piston 38 to which it is rigidlyconnected. Inner oil tube 54 rotates when the runner 12 is rotated andslides up or down as the piston 38 is moved vertically.

Surrounding the inner oil tube 54 and spaced therefrom is an outer oiltube 62 which communicates at its upper end with compartment 52 andextends downward through the main generator shaft 46 to communicate withthe upper end of cavity 64 of the blade servomotor casing 36. The outeroil tube 62 is rotatable '7 within a packing box 66 at its upper endwhich prevents the escape of fluid from the compartment 52 exceptthrough the space provided between the inner oil tube 54 and the outeroil tube 62. The outer oil tube 62 rotates with the main shafting butdoes not move up 75. and down with piston 38.

Blade. control. valve 14. is stationarily mounted rela tive to thegenerator 10, inclose proximity thereto and also in close proximity to,or forming a part of.or an appendage to, the governor. Blade controlvalve 14 comprises a housing 68 to which the ends of a number of fluidconduits are fixed. One conduit 70 extends between valve port 72 ofvalve 14 and compartment 50 of the oil head. Another conduit 74 extendsbetween valve port 76 of vaive 14 and compartment 52 of the oil head. Itwill thus be seen that by means of conduit 70, compartment 56 of the oilhead, and inner oil tube 54, the blade control valve may behydraulically connected, normally, to the blade servomotor 18 on thelower side of piston 38 and that, by-means of conduit 74, compartment 52and outer oil tube 62, the blade control valve may be hydraulicallyconnected to the blade servomotor 18 on the upper side of piston 38.

Pressure conduit 78-is connected at one end to valve port 89 and theother end thereof is connected to a suitable source of hydraulicpressure such as a pump or air loaded pressure tank, not shown. Valve.port 82 communicates with a fluid return conduit 84 which communicatesat its other end with a sump tank at atmospheric pressure in accordancewith conventional practice. The valve housing 68 has a cylindrical valvesleeve 86 within which a valve piston 88 is slidable axially. The sleeve86 has suitable conventional openings therein as shown in Fig. 1 whichcommunicate through cored openings or ports in the valve housing.

Valve piston 88 is actuated by a piston rod 90 which extends from thepiston 88 into the upper housing 92. One end of floating lever 94 ispivotally connected to the upper end of piston rod 90 and the other endthereof is pivotally connected to the lower end of connecting rod 96.Intermediately of its ends, floating lever 94 is pivotally connected bya pin 98 to cam roller mounting assembly 1%. Assembly 1% is providedintermediately of its ends with a guide block 102 slidably mounted formovement between suitable vertical members within the housing 92 asclearly shown in Fig. l.

Rotatably connected to the lower end of assembly. 190 is a cam roller194, the position of which is controlled by a gate-blade cam 106 whichis slidable horizontally relative to the housing 92. When, for example,the wicket gates are moved by the governor, such movement of the gatesvaries the position of the gate-blade cam 106. For example, as the gatesare moving in opening direction the earn 106 will be moved toward theright as viewed in Fig. l, as indicated by the arrow insaid figure,

inasmuch as said cam 196 is connected by a suitable link 108 to anyconvenient movable means on said gates which i will effect the desiredmovement of the earn 166.

Pivotally supported intermediately of its ends by hearing pin lid whichis fixed relative to the generator 10,

for example, is a compensating lever 113 which is pivotally connected atits opposite ends respectively to the upper end of connecting rod 96 andthe lower end of a second connecting rod 112. The upper end of secondconnecting rod 112 is pivotally connected to one end of a secondcompensating lever 114 which is pivoted intermediately of its ends abouta pivot pin 116 fixed relative to the upper end of the casing 48 of theoilhead 16. The other end of the lever 13.4 is pivotally connected to ashort connecting rod 113, the latter being also pivetally connected atits lower end by a pin 120 to. the upper end of inner oil tube 54.

Referring particularly to Figs. 2 and 3 for a betterillustration'thereof, it will be seen that the confining housing (it),with which the inner oil tube 54 communicates at its lower end, is'secured at its perimeter to theupper surface 124 of piston 33. One ormore sets'of interconnected pairs of fluid ports 126 and 127 extendthrough the piston 33 for purposes of permitting fluid to pass from the.lower end of inner oiltube 54 to thelower compartment 128 within theblade servomotor casing 36.

Under. normal. conditions, the passages 126 and 127' are open.so asfreely to. permit fluid under. pressure to be directed against the lowerface or end of piston 38, whereupon movement of the blades toward openposition will either be prevented by the oil under pressure within thelower compartment 128 or, if the pressure is sufficient, it will causethe blades to move in closing direction; Itwillbe understood of coursethat fluid will, under normal circumstances, also be within the cavityd'in the:uppcr: portion of the servomotor casing 36. In general,however, when the turbine is set by blade control valve 14 to maintainthe blades 22 at a desired pitchtoproduce a predetermined speed requiredby the governor in the control system for the generator 10, the pressureof thehydraulic fluid against the lower end or underface' of the piston38 is positive and adequate to equal or exceed the force tending to urgethe piston 38 downward due to the inherent unbalance of the blades 22,as well as the hydraulic forces imposed against said blades torotate therunner 12.

In the illustration of the valve in Fig. l, the valve piston, 88 isdisposed in neutral position whereby pressure through port 80 isnullified due to the valve piston 88 closing; the valve ports 72 and 76from contact by fluid under pressure from valve inlet port The fluidunder pressure within the conduits 7t) and 74, as well as within thechambers 54 and 52 and the inner and outer oil tubes 54 and 62, willmaintain the piston 33 in the: position illustrated in Fig. l or anyother desired position as dictated by the governor. Rotation of therotor of the generator 10 by the runner 12 will continue at the speedand the load afforded by the pitch of the blades 22 illustrated in Fig-1, said pitch being dictated by the governor as referred to above.

Assuming, however, that the load requirements of the generator 10 arevaried, the gates will either be opened more fully or moved towardclosed condition automatically as the situation requires. Such movementwill shift the gate-blade cam 106 and cause the valve piston 88correspondingly to be shifted as a result of vertical movement of theroller 104 engaging the cam 106 and thereby cause movement of floatinglever 94. Hydraulic fluid pressure from conduit 73 will then be causedto flow through either conduit 79 or 74 and thence through either inneroil tube or outer oil tube 62 to cause the piston 33 to be moved eitherupward or downward and thereby correspondingly vary the pitch of the.blades 22 as required by the new load condition on the generator.

As the blades 22 are moving about their axes an amount adequate to drivethe. generator 16. at the rated speed and optimum efiiciency under thenew load conditions, the compensating mechanism comprising pin 120,levers 113 and 114, connecting rods 96 and 112, and floating lever 94are actuated by the axial movement of the upper end of inner tube 54 tore-center the. valve.

piston 88 after movement thereof in either direction for the purposesdescribed above. When said piston 88 is so re-centered, no furthermovement of the blades 22 relative to their pivots can take place.

Assuming, for example, that the generator while operating under anygiven load at rated speed is suddenly disconnected from its load such asby opening the main switch, the governor normally will be affected insuch.

a manner as to actuate the wicket gates toward the closed position, thusshutting down the unit. Substantially simultaneously, but with a slightlag, the blades would thereby be rotated about their trunnions towardthe closed positions thereof. If, however, through some fault in thegovernor or normal control mechanism or the pressure system, the wicketgates should not move as normally intended, runaway speed of the turbineand generator amounting to as high as three times normal speed willoccur and both the turbine and generator must be designed at present onthe basis that this maximum runaway speed will occur.

As s'tated above, by way of example, the usual maximum runaway speedconsidered for purposes of design is approximately within the rangebetween two and onehalf and three times normal speed. Thus, were itpossible to provide runaway speed limiting means which would function insuch a way and particularly automatically so as to positivelysubstantially limit the amount of maximum runaway speeds occurring underthe foregoing circumstances or any other circumstances tending toproduce runaway speeds, it will be seen that the cost of generatorswould be materially reduced, though maintaining the same factors ofsafety, as compared with the present cost of generators which areusually built to sustain the aforementioned maximum amounts of runawayspeeds.

Runaway speed limiting mechanisms It is the principal purpose of thepresent invention to provide a number of different embodiments ofrunaway speed limiting means or mechanisms which have been developed andarranged to function automatically upon overspeeds in excess of apredetermined amount occurring so as to free the blades from the controlof the normal positioning means and permit or cause movement of theturbine blades 22 toward their fullest contemplated open position,thereby providing a greater blade opening which produces a lower maximumrunning speed. This will result in material limitation in runaway speedof the turbine and the generator rotor driven thereby. The need for suchrunaway speed limiting mechanism, in addition to the normal bladecontrol and positioning mechanism and operable to function independentlythereof when overspeeds in excess of a predetermined amount occur, isdue to the fact that the blades normally cannot move freely to thefullest permitted open position thereof while controlled by said normalmechanism. For example, when the piston 88 of valve 14 is centered,hydraulic fluid cannot flow from one side of piston 38 of the servomotorto the other nor be relieved to the sump, and the blades 22 will behydraulically locked against pivotal movement.

Further, under normal speed control of the turbine, and assuming saidnormal control mechanism is functioning properly, if overspeed shouldoccur, the governor will cause movement of control valve piston 88 to aposition to permit flow of hydraulic fluid from the pressure source tolower cavity 128 of the servomotor and from upper cavity 64 thereof tosump, thus closing the blades rather than opening them.

'Still further, under normal operation, the governor which controls theoperation of the cam 106 to actuate the normal blade control valve 14includes fly-balls which, upon overspeed occurring, cause the gates toclose to reduce or completely shut olf the flow of water to the bladesof the turbine runner. Thus it will be seen that the normal controlmechanism, on disconnection of the unit from its load and as a result ofthe consequent overspeed, will function to close the wicket gates, andthereby through the gate blade cam and other mechanism illustrated inFig. 1, for example, also simultaneously close the blades. However, itis the closing of the gates which reduces the turbine speed, not theclosing of the blades, since the closing of the blades per se actuallywould tend to increase the speed. Now, it will be obvious that if thenormal control mechanism through a fault fails to close the gates, theblades will be left at whatever position they were in when the originaloverspeed occurred because control valve 14 is on center and the bladesare therefore hydraulically locked, therefore maximum runaway speed ofthe turbine will occur, possibly as much as three times normal. 7

The various embodiments described hereafter are not equivalents sincethe same have particular advantages respectively under variousconditions of use and related.

structure. In all of the preferred embodiments of control mechanismutilizing the present invention, the inherent 10' unbalance of theblades 22 is utilized to insure movement thereof toward the fullest openposition of the blades permitted by the actuating mechanism when runawayspeeds are sustained by the turbine in excess of a predetermined amount.However, in certain of the embodiments such inherent unbalance, whileadvantageous, may not be essential.

A common characteristic of all species of runaway speed limiting speciesto be described hereinafter is that the action thereof is initiated bythe turbine reaching a selectable predetermined speed above normal,either directly, or indirectly in response to conditions arising in oraffecting the turbine or its controls as a result of said predeterminedspeed above normal. This predetermined speed above normal may be variedselectively from a relatively small amount to the maximum practicalamount. The amount will depend upon the specie of runaway speed limitingmechanism selected for relieving the pressure of the hydraulic fluid onthe underside of the blade servomotor. Such relief may be accomplishedeither by directing the said hydraulic fluid to the sump or by bypassingit to the upper side of the blade servomotor. Such bypassing may beaccomplished either directly through the piston or around the same, orbetween the conduits to and from the servomotor. Various embodiments ofthe invention are illustrated and described hereinafter to achieve theforegoing objectives.

In the specific embodiment illustrated in Figs. 1 through 3, one type ofmechanical runaway speed limiting mech anism is incorporated in thepiston 38 of the blade servomotor 18. The larger scale illustrations inFigs. 2 and 3 best illustrate said embodiment of the invention. It willbe seen that this embodiment of runaway speed limiting means comprisesone or more slide valves 13% mounted for reciprocable movement radiallyof the piston 38. Each slide valve has an integral head 132 reciprocablewithin a radial cavity 134 of the piston 38, the outer end of saidcavity 134 being closed by threaded plug 136. Preferably, a compressedspring 138 extends between the plug 136 and the inner end of a suitablecavity extending into the head 132 of the slide valve 130, as clearlyshown in Figs. 2 and 3. The inner end of the slide valve 13% actuallycomprises a valve closing means which is arranged, when the slide valve130 is moved toward the left as viewed in Fig. 2 to the position shownin Fig. 3, to close the fluid passage, consisting of ports 12b and 127,through the piston 33. It will be understood of course that the bladeservomotor 18 and piston 38 is rotated at the same rotational speed asthe runner 12 and centrifugal force will be developed by such rotation.This centrifugal force will be imposed upon each slide valve 130 inopposition to the force of the spring 138 acting against each valve tomaintain the slide valve 130 in open position as illustrated in Fig. 2.However, spring 138 is selected so as to have sufficient force towithstand centrifugal forces developed during normal operational speedsof the runner and servomotor but, when overspeeds of a predeterminedamount occur, the centrifugal force developed by such speeds and imposedupon each slide valve 139 will be sufiicient to overcome the force ofeach valve spring 138 and thereby force the slide valve 130 to moveradially outward to its closed position illustrated in Fig. 3. Thisthereby closes the fluid passage from the inner fluid tube 54 to thelower side of piston 38 and opens a passageway for fluid from the lowerside of the piston to the upper side thereof through ports 127 and 142as clearly shown in Fig. 3.

Each slide valve 13% has a passage 144i extending axially thercthroughto permit the passage of hydraulic fluid or air or a combination thereoffreely from one end of the valve to the other, thereby insuring that noimpediment is offered to the movement of the valve member 130 by vacuumsbeing established, for example, at either end of the valve member.

It will be remembered that fluid under suffieient pressure I openpositions.

11 within lower compartment 128 of the blade servomotorv 36 and normallyforced against the lower side of the piston 38 prevents movement of theblades 22 toward their Thus, when a passageis provided through thepiston 38, the fluid within lower compartment 128' which normallyprevents movement of the blades-toward the open positions thereof is nolonger confined and, upon passing through ports 127 and 142 in thepiston 38, permits the inherent unbalance of the blades. 22 to move thesame toward their fullest permitted open position. Such movement of theblades carries the piston 38 toward the lower end of the servomotorcylinder. Said opening of the blades 22 decreases the speed of therunner 12 as described herein above to that corresponding to the bladeangle to which the blades have been moved by said inherent unbalanceand, upon. the speed being reduced, the spring 133 associated with eachslide valve 130 will restore the valve to the normal position thereofshown in Fig. 2. If the condition which orignially caused the speed toexceed said predetermined amount has not been obviated by the time tic,aforementioned operation has been completed, any succeeding increase inspeed above the aforementioned predetermined speed will again open thevalve 130 in the piston 38 as described above and the cycle of movementsalso described above will again occur and the maximum runaway speed willbe limitedto that corresponding to the angle to which the blades havebeen moved by their inherent unbalance. The fault in the normal controlmeans which made runaway speed pos sible might be such that it can notbe corrected with the unit rotating. If this is so, the unit can bebrought to rest by closing-the wicket gates by manual control or byclosing the heat gates at the intake.

There will be no relative rotation between the piston 38 and thecylinder casing 36 of the servomotor, although there will be relativesliding movement in a direction axially of said cylinder. Thus, ifdesired, suitable openings may be formed in the wall of the cylindercasing 36 for purposes of permitting access to the valve 130. Suchopenings are not shown in the drawings but it will be readily understoodthat some appropriate form of opening may readily be made in the casingwall, said opening being closed by an appropriate pressure resistingclosure.

Preferably, one such opening should be provided in the cylinder wall foreach slide valve 130. It will be noted that the slide valves 13% andsprings 138 are so constructed that they may readily be withdrawnradially outward from the piston 38 when the plug 136 is removed.

it will also be noted that Fig. 2 illustrates one valve member 130 infull lines while a second one, in the right hand portion of Fig. 2, isillustrated in phantom, it being understood that any desired number ofsuch valves may be used in conjunction with a corresponding number ofsets of ports 126, 127 and 142 through the piston 33. In the preferredconstruction, the valves 13!) are arranged, when a plurality are used,so as to balance each other relative to the piston 38 and therebyminimize any outof-balance effect which might otherwise be caused by useof such valves.

The above described pressure by-passing mechanism used for purposes ofpermitting the blades to open at speeds above a predetermined amountwill function regardless of the position of the control valve 14 as thehydraulic fluid need not flow through said valve in either directionduring the functioning of the above described fluid pressure by-passingmeans in the piston 38. For example, assume that the valve piston 88 isin a position such that hydraulic fluid under pressure from conduit 73can enter the lower compartment 128 of the blade. servomotor casing 36so as to be disposed against the lower end of the piston 38 and theupper cavity 64 of the casing 36 is connected to the fluid returnconduit 34 for passage to sump. Assume further that the valve piston 88would stick in this position. When a speed in excess of saidpredetermined amount occurs, such sticking of the valve pistontsflwouldznot. inany way, affect by-passingof-the oil through the servomotorpiston 38 because the, slide.

Vales are free to move irrespective of thesetting and effect of thecontrol valve 14 and thereby efiect passage.

of hydraulic fluid through the piston 38, thus. permitting the piston tolower and the blades 22 to movedoor toward open position due to theinherent unbalance thereof.

Conversely, if the upper end of the-piston were subjected to full oilpressure and the lower. end of the. piston were connected to sump, theblades of therunner would naturally move to full open position even ifno oil by-pass: If such. by-pass' means. is installed in said piston,however, the hydraulic. fluid.

means is installed in piston 38.

pressure would immediately tend to be equalized in cavilies 6-! and 128,thus permitting the blades to open due to their inherent unbalance,regardless of what the nature of the fault in the normal controlmechanism maybe.

Displaced oil in lower cavity 128 will pass to upper cavity 54 inaccordance with the downward movement of piston 38, it being understoodthat displacement aboveand below the piston for any given pistonmovement will be equal or any diiference readily may be compensated typeresponsive to excessive hydraulic pressure developed as a result ofoverspeeds in excess of a predetermined amount tending to move theblades 22 toward open position by reason of the inherent hydraulicunbalance thereof. Such movement is prevented at normal speeds byhydraulic pressure against the lower side of the piston 38 but excessiveoverspeeds produce abnormal pressures within the lower cavity 128 of theservomotorcas= ing 36.

In Fig. 4, the mechanism is illustrated in normal'operating condition.by-pass conduit is connected at its opposite ends respectively to theupper cavity 64 in the upper end of cylinder casing 36 and the lowercavity 128 in said'cylinder casing. Connected in said by-pass conduit146 is' a pressure relief valve 143 including a compressible spring,

150 acting against a valve piston 152'which co-actswith valve seat 154.Valve piston'152 is provided with suitable guide fins 156 to insureaxial movement ofthe valve piston.

Under conditions where overspeeds occur in excess of a predeterminedamount, for example, about 75% in excess of normal speed, the excessivepressure developed within the lower cavity 128 will react against valvepiston 152, which is normally closed against the valve seat 154, andforce said piston 152 to open position thereof, illustrated in Fig. 5,compressing spring 150 as a result. It will be understood of course thatthe spring 150 is suitably adjusted as to pressure by the adjustablethreaded plug 158 to permit the same to be compressed and thereby effectopening movement of piston 152 upon a predetermined amount of pressurebeing exerted against the piston 152 from cavity 128.

As will readily be seen from Fig. 5, when the valve piston 152 is movedto open position, fluid within cavity 128 will flow through the valveopening and the by-pass conduit 146 into upper cavity 64, taking up thespace vacated by reason of the piston 38 having moved toward the runner.In any case this will permit the piston 38. rapidly to lower due to theinherent unbalance of the blades 22 tending to pull the piston 38downward.

As in regard to the embodiment shownin Figs. 1

through 3, it will be. understood that, for a given piston In thisfigure, it will be seen that a.

movement within the servomotor casing, the increase in fluid volume inupper cavity 64 must be at least equal to the decrease in lower cavity128. Any difference readily may be compensated for by appropriatedetails in design well known in the art.

Upon the blades opening as the result of said tendency toward fullestpermitted open position and in due course reaching same, the speed ofthe turbine and generator will be reduced and such opening of the bladeswill be possible regardless of the setting of the control valve 14 orany faulty operation of the normal control mechanism.

When, by reason of said reduction in speed, the pressure against valvepiston 152 is reduced so as to be less than the force exerted by spring150, said spring will move the valve piston 152 to its closed positionshown in Fig. 4 and the turbine will then be in condition to functionnormally as dictated by the control valve 14 and the governor in thecontrol system as described herein above. Suitable locking means such asa nut 160 may be used to secure the threaded plug 158 in desiredcalibrated position and the outer end of the threaded plug covered by acap 162. The compression of spring 150 is initially set such that thevalve piston 152 can not open unless the pressure in cavity 128 exceedsthe normal maximum pressure that might be required to pitch the bladeswhile the unit is operating at rated speed or slightly above.

Notches 164- may be provided in the walls of piston 38 to preventobstruction of the outlet of oil conduit 146 when details ofconstruction so require. Also, while in Fig. 5 the piston 38 is shown atthe fullest extent of its normal travel in normal opening direction, itwill be understood that in cases where it is desirable to have theblades go to a greater pitch than normal upon runaway speed occurring,the casing 36 of the servomotor 18 would be made appropriately longer topermit such greater movement of the piston.

Still another embodiment of runaway speed limiting mechanismincorporating the principles of the present invention is illustrated inFigs. 6 and 7. This embodiment utilizes electrical means to interconnectcertain of the elements of the control system during normal speedoperation of the turbine and generator. However, upon overspeedconditions in excess of a predetermined amount occurring, the circuit ofelectrical actuating mechanism is broken in response to said overspeedconditions, whereupon the blade control mechanism, comprisingessentially a by-passing valve, is actuated in such a manner as toeffect movement of the blades toward open position and thereby limit themaximum runaway speed of the turbine and generator to that correspondingto the open position to which the blades have been moved by theaforementioned inherent unbalance thereof.

Referring to Fig. 6 particularly, the control valve 14 is illustrated inlarger scale than in Fig. 1 and fragmentarily. Further, it will beunderstood that the control valve controls the flow of hydraulic fluidthrough con duits similar to conduits 7t) and 74, illustrated in Fig. 1,to the inner and outer oil tubes 54 and 62, the latter not beingillustrated in Fig. 6. In the embodiment shown in Fig. 6, the lever andlinkage system illustrated in the upper portion of the figurecorresponds substantially to similar mechanism shown in Fig. 1 and thefunc tioning of both linkage and lever mechanisms is similar. hydraulicpressure developed during overspeed conditions in excess of apredetermined amount is by-passed through or around the piston 38,thereby tending to balance the pressure in cavities 64 and 128 forpurposes of permitting the blades 22 to move toward or to fullestpermitted open position. The embodiment shown in Fig. 6 however does notrequire the use of such pressure bypass means through or around thepiston of the servo- In the embodiments shown in Figs. 1 through 5 vmotor 18. This embodiment affords a complete relief to atmosphericpressure of the lower cavity 128, said relief being instigated by anelectrical centrifugal switch responsive to the R. P. M. of the unit.

In the preferred structure illustrated in Figs. 6 and 7, an electricalcentrifugal switch 166, calibrated to be responsive to generator R. P.M. in excess of a predetermined amount, is driven by the hydroelectricunit, preferably mechanically, so as to be affected by said speed. Theswitch 166 and the circuit thereof is only diagrammatically shown inFig. 6. However, said c-ircuit contains contacts so as to interconnectthe switch 166 in a circuit comprising a source of current 168 and themagnets of a solenoid type clutch 170.

As shown in Figs. 6 and 7, the clutch 170 comprises a plurality ofelectro magnets 172, the windings of which are electrically connectedwith each other and with a source of current 168. Pivoted latches 174are arranged so that one end of each latch, when held by magnetic forceagainst the magnets 172, is disposed within an annular groove 176 formedin the lower end of a vertically movable piston rod extension 178,pivotally connected at its upper end to floating lever 94. As is clearlyshown from Fig. 6, a solenoid clutch weight 177 is fixed to the upperend of piston rod and it will be noted that said weight is relativelymassive so as to be capable of readily moving the valve piston 88downward by gravity when the weight 177 is disconnected from piston rodextension 178.

The centrifugal electric switch 166 is preferably of the adjustable typeand responsive to any selected rotational speed of the hydroelectricunit within an appropriate range. It is contemplated that said switchmay be set to open upon a predetermined speed being developed by theturbine and generator 10. Upon said predetermined speed being attained,which is in excess of normal speed, the switch 166 will open and therebybreak the circuit to the electromagnets 172. Deenergizing said magnetswill result in the weight 177 quickly moving the latches 174 about theirpivot pins 175 to permit disconnection thereof from extension 178,thereby permitting the weight 177 to move the valve piston 88 to thelower position thereof shown in Fig. 7. Such movement of the valvepiston downward is arrested by suitable stop means such as blocks 179which directly engage the unders'urface of weight 177 as shown in Fig.7.

When the turbine and generator rotor are rotating at normal speeds, orup to the speed for which the switch is set, extension 178 and pistonrod 90 will be interconnected by the solenoid clutch so as to maintainthe valve under direct control by the linkage and lever systemillustrated in Fig. 6, the same being primarily directed by the governorthrough cam 106. As described above in regard to the embodiments shownin Figs. 1 through 3, the position of cam 106 normally is varied inaccordance with movement of the wicket gates so as correspondingly tovary the pitch of the blades 22. Thus, under normal operating conditionswithin normal speed ranges, i. e., from zero speed up to approximately50% above normal speed, for example, clutch 170 will maintain the valvepiston 88 connected to the linkage and lever control mechanism fornormal operation thereof by the governor through cam 106. Under thesenormal conditions when the blades 22 are set at a certain pitchcorresponding to a desired speed and load on the turbine, the valvepiston 88 will be maintained in neutral position illustrated in Fig. 6or will otherwise function as dictated by the governor. Hydraulicpressure from conduit 78 will be held inactive or be routed as dictatedby the governor. When the valve piston 88 is in neutral position as inFig. 6, it closes the ports 72 and 76 in the control valve 14, wherebyservomotor piston 38 has hydraulic fluid at both ends thereof serving tohold the piston 38 against movement and thereby preventing the pitch ofblades 22 from changing.

Upon an overspeed of a predetermined amount occurring from any of anumber of causes of abnormal nature, the centrifugal switch 166 willfunction to disconnect the circuit of the solenoid clutch 170 asdescribed above, whereupon weight 177 will force the valve piston 88 tomove to the lower position thereof shown in Fig. 7. Lowering valvepiston 88 to the position shown in Fig. 7 connects lower cavity 128 inblade servomotor casing 36 to the sump tank of the hydraulic pressuresystem, by means of holes through piston 38, confining housing 60, inneroil tube 54, oil head fluid compartment 50, conduit 70, port 72,longitudinal ports 180 in piston 88, port 82, and conduit 84. Since thesump tank is open to atmosphere and is at an appreciably lower elevationthan blade servomotor 36, downward movement of piston 38 is facilitated.

There being a positive inherent unbalance of the runner blades 22 inopening direction at overspeeds, said blades will positively open tofullest permitted extent quickly by reason of the relief of pressure onthe underside of piston 38. This will positively result, regardless ofwhat fault occurred in the normal control mechanism which permitted theoverspeed initially to occur.

Rotation of the turbine will continue at speeds less than thepredetermined overspeed for which electrical switch 166 was set untilsuch time, as the water is shut off from the turbine by some means suchas a head gate. Thereupon the fault may be remedied, solenoid clutch1701a. stored to interconnect with valve piston extension 178-, solenoid172 re-energized, and all other conditions restored to normal and theunit restarted.

The mechanism illustrated in Fig. 8 is identical in pur pose to thatshown in Figs. 6 and 7, i. e. upon runaway speed in excess of apredetermined maximum, it will effect a complete relief to atmosphericpressure of the lower cavity 128, said relief being actuated by anelectrical centrifugal switch responsive'to the R. P. M. of thehydroelectric unit. The difference between the mechanism in Fig. 8, andFigs. 6 and 7 is only in the nature of the respective gate-blade cams.Both types of cam are commonly used in the normal control mechanism ofadjustable blade propeller turbines and the reason for illustrating themboth is merely to show that the present in-. vention, being an additionto the normal control mechanism, may be applied regardless of which typeof cam is used.

The mechanism illustrated in Fig. 8 is similar to that shown in Figs. 6and 7,. except that in the mechanism shown in Figs. 6 and 7, the earn166 is linearly actuated by the governor in unison with movement of thewicket gates. Said cam 182 may be rotated by rotation of cam shaft 183about fixed center 184, as dictated by the governor by means of lever185 and connecting rod 186 or as otherwise convenient.

The normal operation of the control mechanism, i. e. at normal rotativespeeds of the hydroelectric unit below a predetermined overspeed, issimilar to that described herein relative to Figs. 6 and 7, saiddescription being modified only in regard to the manner in whichrotation of cam 182 actuates piston rod extension 173 which is asfollows:

When, for example, a load increase upon the generator occurs, thegovernor mechanism rotates cam 182 clocle wise referring to Fig. 8. Thisforces down cam roller 188, which is rotatably connected with floatinglever 94, pivoting about the pin connecting its outer end toconnectingrod 96, shown in Fig. 6, and also forcing piston rod 94 pivots about theaxis of cam roller 138, thus raising connecting rod extension 178, theengaged solenoid clutch 170, connecting; rod and valve piston 88,recentering the same with valve port 80 and thereby holding the runnerblades 22 in the position corresponding to optimum efiiciency of theunit at the new load. Compressible spring 189 functions merely to holdcam roller 188 against cam 182 at all times, said spring being supportedbetween upper spring cap 190 supporting the cam roller and the lowerspring cap 191 which pivotally rests upon or against a fixed support192. However, if the unit is disconnected from its load and the normalcontrol mechanism of the hydroelectric unit fails to function properly,resulting in overspeed of an amount in excess of predetermined maximumfor which electrical centrifugal switch 166 is set, then the blades 22will go to the maximum permitted full open position in the same mannerand for the same reasons and purposes as herein described in connectionwith Figs. 6 and 7.

In the foregoing description pertaining particularly to Figs. 6, 7 and8, electrical switch 166 is described as being of the centrifugal type.This type is well known in the art as having mechanism rotatable at aspeed proportional to, in this instance, the speed of the hydroelectricunit, and containing electric contacts which either open or close,whichever may be more desirable, in response to certain degress ofcentrifugal force induced by the rotation of the switch elements by themachine driving said electrical centrifugal switch.

As another related species of this embodiment of the invention, saidelectrical switch 166 could be of a type reactive, for example, tohydraulic fluid pressure, i. e. an electrical pressure switch 167.Switch 167 is such that its contacts open upon pressure in any part ofthe pressure system, which is hydraulically connected at all times withthe lower cavity 128 in casing 36, exceeding a predetermined maximumvalue, thereby relieving to sump any pressure holding the blades frommoving in opening direction. Considering Figs. 6, 7 and 8 and thedescriptions relating thereto to be the same as above but substitutingelectrical pressure switch 167 for electrical centrifugal switch 166, itwill be seen that the remainder of the equipment will function similarlyand with a similar end result as when centrifugal electrical switch 166is used to control the clutch circuit.

Regarding the embodiment shown in Figs. 6 through 8, it will be evidentthat release of pressure under the servomotor to sump as a result ofmovement of the control valve will cause oil to go to sump by gravityfrom under the servomotor piston. The weights of the piston, theoperating rod, and the crosshead, all operating downward by gravity, asWell as the weight of oil above the piston and some pressure of the oilabove the piston, when pressure under the servomotor is released tosump, will all aid in elfccting downward movement of the cross head.Thus, in the embodiments shown in Figs. 6 throughout 8, the blades 22 ofthe runner 12 may be balanced for movement about their axes, rather thaninherently unbalanced toward open position as in certain of the otherembodiments shown and described herein, and the blades will neverthelessbe caused to move to open position to reduce the runaway speed of theunit.

Another embodiment of runaway speed limiting mechanism of this inventionis illustrated in Fig. 9, this embodiment being similar to that shown inFigs. 4 and 5 in that the hydraulic blade operating fiuid is by-passedfrom the high pressure to low pressure passages at a different location,namely in the oil head 16 rather than at the blade servomotor 18.

Regarding the embodiment shown in Fig. 9 and, as described above inregard to Fig. l, hydraulic fluid compartments 50 and 52 in the oil head16 are separated from each other and respectively communicate with theinner oil tube 54 and outer oil tube 62. These compartments areseparated by a partition 193. In order to by-pass excessive hydraulicfluid pressure developed during overspeed conditions in such manner asto permit the blades to move toward the maximum permitted open positionsthereof, it is only necessary to hydraulically interconnect lower cavity128 and upper cavity 64 of blade servomotor casing 36. This may beaccomplished by any of a number of means, in response to excessivepressure in lower cavity 128, one means being as illustrated in Figs. 4and 5, another, which is directly responsive to excessive rotationalspeed of the turbine, is shown in Figs. 1, 2 and 3, and still another,shown in Fig. 9, essentially comprises a by-pass between conduits 70 and74 at a convenient location.

When lower cavity 128 is subjected to excessive fluid pressure developedduring overspeed conditions above a predetermined limit, uppercompartment 50 of the oil head will be subject to the same pressure. Ofcourse, when the generator and turbine are operating at normal ratedspeeds, there will be no excessive pressure anywhere in the system.

The fluid by-passing means of the embodiment shown in Fig. 9 comprises apressure responsive valve assembly 194. In the specific embodimentillustrated, a valve seat ring 196 is fixed within a suitable openingformed in the partition 193. A valve seat 198, preferably spherical, isformed in the valve seat ring 196 and a slidable valve piston 200 has acomplimentary surface 202 which conforms to the valve seat 198. The seatring 196 also preferably has a bearing sleeve 204 integrally securedthereto by radial ribs 206 between which are ports 207. The valve piston200 has a bearing surface 208 which slides on the bearing sleeve 204 toguide its axial movement. Bearing sleeve 204 also slidably receives theinner oil tube 54 as clearly shown in Fig. 9 and permits axial as wellas rotatable movement of said oil tube relative to the bearing sleeve204. Valve piston 200 normally is forced upward by a compression spring210, the lower end of said spring resting against a relatively fixedseat 212. The spring 210 is selected so as to exert a maximum forcesubstantially equal to the force upon valve piston 200 from uppercompartment 50 that would occur at a predetermined overspeed.

When the turbine and generator are operating at normal speeds the valvepiston 200 will be maintained in closed position by the action of spring210. Under these circumstances, the control mechanism and oil flowthroughout the pressure system will function just as though the pressureresponsive valve assembly were not present, i, e., just as though theoil head were constructed as shown in Fig. 1, said functioning beingwell known in the art. However, should the electrical load on thegenerator suddenly be disconnected from the same and if, for any reason,runaway speed occurs in excess of a predetermined amount, the inherentunbalance of the blades pulls down abnormally upon piston 38, creatingexcessive pressure in lower cavity 128 and upper compartment 50.

When the pressure in upper compartment 50 increases above apredetermined limit, which corresponds also to the calibrated setting ofthe spring 210, the valve piston 200 will be separated from the valveseat ring 196, thereby permitting fluid under excess pressure fromcompartment 50 to flow into compartment 52 and from thence through outeroil tube 62 to upper cavity 64 of the servomotor casing 36. Thus ahydraulic circuit or passage will be provided for the hydraulic fluidfrom the underside of piston 38 to the upper side, resulting in the turbine blades 22 being able to move in an opening direction by reason oftheir inherent unbalance at higher than normal rotational speeds. Thespeed of the turbine and generator will thereby be prevented fromexceeding a predetermined limit.

Following such reduction in speed of the turbine and generator, it willbe understood that since the excessive fluid pressure in uppercompartment 50 has been re duced below the limit at which the valvepiston 200 opens, said valve will close so as again to seal compartments50 and 52 from communication with each other.

18 The above described cycle may reoccur but at no time will the speedof the unit exceed a predetermined limit. If necessary, the water may beshut off from the turbine by means of a head gate or otherwise, tolocate and correct the fault in the normal control mechanism whichoriginally permitted the overspeed, and the unit may then be re-started.

One further embodiment of runaway speed limiting mechanism, utilizingmechanical principles, is illustrated in Fig. 10. In this embodiment, noother type of runaway speed limiting mechanism such as herein beforedescribed is required and either a conventional blade servomotor 18,with the customary type of piston therein may be utilized, or a gearedelectric motor or any other suitable device may be used to pitch therunner blades 22 under normal conditions of operation. When runawayspeed conditions occur, as described above in regard to the variousother embodiments of the invention, the same inherent unbalance of theblades as Well asthe unbalance of the hydraulic force imposed upon saidblades also exists and tends strongly to move the blades toward theirfullest permitted open position but the fluid pressure acting againstthe lower end of the servomotor piston or mechanical leverage of thegears in case of electric motor drive normally prevents such movement.In the case of the servomotor type of blade operation, the hydraulicpressure acting against said lower end of the piston likewise preventsdownward movement of the piston rod 32 and the cross-head 40. The links44 and the link bolts 42, which interconnect the cross-head 40 and therocker arms 30, serve to maintain the blades at the pitch required bythe governor.

Referring to Fig. 1, under normal operating conditions the force of theoperating mechanism when increasing the blade pitch results in tensionin link bolts 42 and links 44. However, if the cross-head 40 is heldstationary in an axial direction, the blades, due to their inherenttendency to open upon overspeed, endeavor to open and the link bolts 42and links 44 are placed in compression. If, however, the blades 22 shownin Fig. 1 were arranged oppositely to the crank arms 30 thereof, asshown in Fig. 10, the link bolts 42 and links 44 would then be undertension as the result of the unbalance of the blades and other forcestending to move the blades toward a greater open position under runawayspeed conditions. Thus, the latter arrangement is used in the embodimentshown in Fig. 10 for purposes of providing a runaway speed limitingmeans of a mechanical nature.

Whereas in the structure shown in Fig. 1 the link bolts 42 may besecured to the ends of the crosshead 40 by threaded nuts, the embodimentshown in Fig. 10 utilizes a shear pin 214 to secure each link bolt 42 toits arm of the cross-head 40. The shear pins 214 are of such size as tofracture in shear upon a predetermined force being exerted against saidpins. Said predetermined force will be that at which it is desired thatthe blades 22 may be freed for movement to fullest permitted openpositions upon a runaway speed of predetermined amount occurring, suchas to subject the blades 22 to a corresponding force tending to movesaid blades toward their fullest permitted open positions.

The shear pins 214 are adequate to resist operating force imposed uponthe blades 22 at normal speeds. However, when a predetermined overspeedoccurs the pins 214 are sheared and it will be understood that theblades 22 will then move incident to the shearing of the pins 214regardless of the fact that the operating rod 32 remains stationary.

Obviously with this arrangement of the rocker arms 30 relative to theblades 22, the normal control mechanism for pitching the blades would bearranged so that pressure oil would be admitted to the underside ofpiston 38, i. e. to lower cavity 128, and upper cavity 64 would beconnected to the sump when opening movement of 19 the blades isrequired. That is, the crosshead would go up to open the blades and downto close them in normal operation, rather than vice versa.

Furthermore, it will be apparent that if onerrunner blade were in someway stuck such as by foreign matter being lodged, for example, between ablade and the runner hub 28, so that it could not open in response torunaway speed exceeding a predetermined amount, the remaining blades 22of the runner which are not so stuck could go open, thus stillpreventing any degree of overspeed sufiicient to endanger the safety ofthe unit.

In order to restore the turbine runner blades to normal operatingcondition so as again to be controlled by the servomotor 18 followingshearing of the pins 214, it will of course be necessary to reconnectthe link bolts 42 to the arms of the crosshead by replacing thefractured shear pins 214. This can readily be done after the turbine hasbeen unwatered and stopped, by mechanics removing the runner cone 216from the runner 12 so as to gain access to the crosshead 40.

Another embodiment of the shear pin principle is shown in Fig. 11, andmay be incorporated with the various other runaway speed controlembodiments illustrated in Figs. 1 through 9 and described'hereinabove.However, such shear pin principle is embodiable with said other runawayspeed control means for a ditferent purpose than that utilized in theembodiment of Fig. 10. For example, in Fig. 11, wherein the additionalshear pin principle is to be used in conjunction with other runawayspeed limiting means, it will be noted that the exemplary blade 22 isarranged relative to the rocker arm 30 oppositely to the arrangement inFig. 10 but the same as in the arrangement shown in Fig. l. Thearrangement of blades and rocker arms shown in Fig. 1 is the same in thevarious other embodiments of runaway speed limiting means described andillustrated herein with the exception of the embodiment shown in Fig.10.

Referring to Fig. 11, it is therefore assumed that one of the otherrunaway speed control means is utilized in the turbine-generator unitsuch as illustrated in Figs. 1 through 9. Upon the occurrence of runawayspeed conditions in excess of a predetermined limit, the aforementionedother runaway speed limiting means will function to permit the piston 38of the servomotor 18 to be lowered by reason of the inherent unbalanceof the blades 22 and correspondingly to permit or effect movement of theblades 22 either toward or to the fullest permitted open positionsthereof so as to reduce or limit the speed of the turbine and generator.

If the blades are not stuck by reason of foreign matter being lodgedbetween the blades and some member stationary relative to blade pitchingthen, under normal speeds and with the normal control mechanism properlyfunctioning and also under runaway speeds in excess of a predeterminedmaximum permissible limit and with the normal control mechanism notproperly functioning, the

blades will be pitchable in response to either condition,

as required. However, debris of various kinds floating in the head waterimpounded by a dam will sometimes escape the customary trash racks andenter the spaces between the wicket gates and contact the blades of therunner. In fact, if debris of this nature should become lodged relativeto several of the wicket gates so as to obstruct movement thereof whenclosing of the gates is required due to release of the load from theturbine, runaway speed may result from such condition.

Another deleterious effect may occur from the possibility of engagementof debris articles with the runner 22. Said possibility arises from thefact that the inner ends of the blades 22, adjacent the hub 23, aresometimes so shaped that during movement of the blades relative to thehub between maximum permitted open and closed positions, spaces occurbetween said inner ends of the blades and the exterior surface of thehub. Should debris, such as apiece of wood, be trapped in such a ,spacewhen, forexarnple, the blades are disposed at a pitch intermediate oftheir maximum open and closed positions, and runaway speed conditionsoccur which because of one of the aforesaid embodiments cause thepisthough the runaway speed conditions demand movement of the bladestoward full permitted open position, the functioning of the runawayspeed limiting means would be nullified under the foregoingcircumstances wherein one of the blades was wedged against moving tosuch open position and it is remotely conceivable that excessive runawayspeeds then could continue with corresponding harm to the generator orturbine, or both.

To obviate the foregoing possible nullifying of the effect of therunaway speed limiting means, the actuating means for the blades 22 maybe provided with fracturable shear pins 214 clearly shown in Fig. llwhich extend through the crosshead 40 and the lower ends of the linkbolts 42. Upon runaway speed conditions occurring and the runaway speedlimiting means functioning to permit the crosshead 40 to move downward,all of the blades 22 would normally move to the fullest permittedopenposition. However, if one of the blades had a piece of debriswedged, for example, between it and the hub of the runner so as toprevent such movement of the blade toward its fullest permitted openposition, the resistance of said blade to movement would result in shearpin 214 shown in Fig. 11 being fractured so as to separate said bladefrom control by the crosshead. The crosshead 40 would thereupon be freeto continue its downward movement and the rest of the blades could moveto the fullest permitted open positions thereof. Of course, the wedgeblade presumably will remain in its wedged position but the movement ofthe remaining blades to their maximum permitted open positions, forexample, will insure a reduction in the runaway speed of the turbine toa value below the predetermined limit and thereby prevent damage beingsustained by either the turbine or the generator.

As described in regard to the embodiment of Fig. 10, after a shear pinutilized in the embodiment of Fig. 11 has been fractured, it will ofcourse be necessary toshut down the unit for purposes of replacing thesheared or fractured pin 214. However, it will be necessary to shut downthe unit any way for purposes of removing the wedged article of debrisfrom the blade so as to restore the blade to operative conditionrelative to the hub 28 and to correct the fault in the normal controlmechanism which caused the runaway speed initially.

Summary From the foregoing, it will be seen that the present inventionprovides a number of various embodiments of runaway speed limiting meanswhich will function automatically to positively prevent runaway speedsin excess of a predetermined amount occurring in an adjustable bladepropeller turbine and generator unit, said amount being, for example,50% to above normal speed, depending upon the embodiment used, insteadof up to 200% above normal, which the turbine would be capable ofproducing were such embodiments not added to the presently used means ofnormal control. These various embodiments utilizerespectivelymechanical, hydraulic, and electrical principles to insure movement ofthe blades 22 toward or to the fullest permitted open positions thereofdue to the hydraulic unbalance of the blades at speeds above normal.Such movement will cause the maximum 21 runaway speed of the turbine tobe limited to amounts for which it and the generator may be moreeconomically designed in anticipation thereof.

As a result of incorporating any of the above described and hereinclaimed runaway speed limiting means and mechanisms in aturbine-generator unit, the cost of manufacturing such turbine generatorunits is materially reduced as compared with the cost thereof inaccordance with present practice wherein the same are usually designedto withstand runaway speeds of the order of two and one-half to threetimes normal operating speeds. Further, and at least equally important,is the fact that the present invention provides means to insure againstpossible destruction of mechanism frequently worth millions of dollarsat a greatly reduced cost. Such destruction where it has occasionallyoccurred in the past has in most cases been also accompanied by loss ofhuman lives.

As stated hereinabove under the title Runaway Speed Limiting Mechanisms,upon overspeed occurring, when the normal control mechanism isfunctioning properly, the blades will be moved toward or to closedposition, whereas the function of the runaway speed limiting devicesdescribed and claimed herein is to permit the inherent hydraulicunbalance of the blades to cause movement thereof toward or to themaximum permitted open position thereof. Also, whereas normal blademovement may be from 6 to 32 relative to a plane normal to the axis ofrotation of the turbine, when runaway speed occurs, pitching of theblades within a range between 6 to 50 may be desirable in someinstances. In these instances appropriate provision would be made in theop erating mechanism to permit the additional abnormal travel.

As used hereinabove and in the appended claims, the terms runaway speedand overspeed in some instances may seem to be synonymous. However it isintended that runaway speed be considered as the maximum speed for whichthe unit must be designed, whereas overspeed is considered to be anyspeed above the normal rated speed of the unit and up to said runawayspeed. Therefore, overspeed is permissible and is used to actuate therunaway speed limiting devices and may be utilized whether the normalcontrols have functioned or not.

Though a number of embodiments of runaway speed control devices havebeen illustrated and described herein, the same are not consideredequivalents in that they vary as to applicability according to thephysical structure and size of the turbine and to the percentage ofoverspeed at which they will function.

While the invention has been shown and illustrated in its severalpreferred embodiments, and has included certain details, it should beunderstood that the invention is not to be limited to the precisedetails herein illustrated and described since the same may be carriedout in other ways falling within the scope of the invention as claimed.

I claim:

1. A hydraulic turbine comprising a runner having pivotally adjustableblades thereon, the blades and pivots thereof being so connected thatsaid blades are hydraulically unbalanced for movement toward the openpositions of said blades at speeds above normal, and norm-a1 positioningmeans utilizing hydraulic pressure which varies in proportion to thespeed of the turbine, said means being interconnected with said bladesand operable normally to maintain said blades in desired positions ofoperation and vary the same to produce a desired turbine output atnormal speed, in combination with runaway speed limiting mechanisminterconnected with said normal positioning means and includingmechanism responsive to the hydraulic pressure thereof and operable uponsaid pressure attaining a predetermined amount at speeds of the turbineabove normal to free the blades from the control of said normalpositioning means and permit the said hydraulic unbalance of said bladesto move the same 22 toward said open positions thereof, thereby limitingthe runaway speed of the turbine to a value corresponding to that of theopen position of the blades to which they have been moved by saidhydraulic unbalance.

2. A hydraulic turbine comprising a runner having pivotally adjustableblades thereon, the blades and pivots thereof being so connected thatsaid blades are hydraulically unbalanced for movement toward the openpositions of said blades at speeds above normal, and positioning meansinterconnected with said blades and operable normally to maintain saidblades in desired positions of operation and vary the same to produce adesired turbine output at normal speed, in combination with runawayspeed limiting mechanism including electrical mechanism operable inresponse to a predetermined speed condition in excess of the normalspeed of the turbine and interconnected with said normal positioningmeans and operable automatically at speeds of a predetermined amountabove normal to free the blades from the control of said normalpositioning means and permit the said hydraulic unbalance of said bladesto move the same toward said open positions thereof, thereby limitingthe runaway speed of the turbine to a value corresponding to that of theopen position of the blades to which they have been moved by saidhydraulic unbalance.

, 3. The turbine structure set forth in claim 2 further including aspeed responsive switch in said electrical mechanism and said switchbeing responsive to the rotational speed thereof and operative upon saidspeed exceeding a predetermined amount above normal to cause movement ofsaid blades toward said open positions thereof and thereby limit therunaway speed of said turbine to the value aforesaid.

4. The turbine structure set forth in claim 2 further including apressure responsive switch in said electrical mechanism and furthercharacterized by said control means utilizing a hydraulic systemconducting hydraulic fluid under pressure, said switch beinginterconnected with said hydraulic system and responsive to changes inthe pressure therein, said switch being operable upon said pressureincreasing a predetermined amount above normal to cause movement of saidblades toward said open positions thereof and thereby limit the runawayspeed of said turbine to the value aforesaid.

5. A hydraulic turbine including an adjustable blade runner supportedfor rotation about its axis and comprising a hub, a plurality of bladespivotally supported by said hub and said blades and pivots being soconnected that said blades are hydraulically unbalanced for movementtoward the open position of said blades at speeds above normal, andblade positioning means including a hydraulically operated servomotorhaving a piston interconnected to said blades and hydraulic pressure andreturn conduits interconnected between a source of fluid pressure andsaid servomotor, said positioning means also including a control valveconnected between said conduits and operable to direct pressure againsteither end of said piston selectively to vary the positions of saidblades and maintain them in a substantial range of operative positions,in combination with pressure relief means interconnected with said bladepositioning means and upon said turbine exceeding a predetermined speedand developing hydraulic pressure in said system in excess of normalblade control pressures said pressure relief means being operable todirect the hydraulic fluid under pressure from the end of said pistonfunctioning to hold said lades against said movement to the returnconduit, thereby to permit movement of said piston and blades towardsaid open positions thereof and limit the runaway speed of said turbineto a value corresponding to that of the open position of the blades towhich they have been moved by said hydraulic unbalance.

6. The hydraulic turbine structure of claim 5 additionally including anoil head mounted above said servomotor and interconnected with saidhydraulic pressure and return conduit means, and said pressure reliefmeans in said blade positioning means comprising a pressure responsivevalve mounted on said oil head, whereby upon the development of pressurein excess of a predetermined amount in the conduit connected to the endof the servomotor holding the blades against movement in the openingdirection, said valve will open and pass fluid from the said end of saidservomotor to the opposite end thereof, thus permitting said blades tomove toward said open positions thereof to limit the runaway speed ofsaid turbine to a value corresponding to that of the open position ofthe blades to which they have been moved by said hydraulic unbalance.

7. A hydraulic turbine including an adjustable blade runner supportedfor rotation about its axis and comprising a hub, a plurality of bladespivotally supported by said hub and said blades and pivots being soconnected that said blades are hydraulically unbalanced for movementtoward the open position of said blades a speeds above normal, and bladepositioning means interconnected to said blades and including ahydraulically operated servometor having a piston operable to vary thepositions of said blades and maintain them in a substantial range ofoperative positions, in combination with a hydraulic fluid by-pass valvemounted in the piston of said servomotor operable upon said turbinebeing subjected to a selected predetermined runaway speed condition toopen and permit passage of hydraulic fluid from the end of theservomotor functioning to prevent said movement of said blades to theother end thereof, whereupon said blades move toward said open positionsthereof and thereby limit the runaway speed of the turbine to a valuecorresponding to that of the open position of the blades to which theyhave been moved by said hydraulic unbalance.

8. The hydraulic turbine structure of claim 7 further characterized bysaid piston of said servomotor being rotatable with said runner and saidby-pass valve being responsive to and operable by centrifugal forcegenerated by the rotation of said piston at a predetermined speed.

9. A hydraulic turbine including an adjustable blade runner supportedfor rotation about its axis and comprising a hub, a plurality of bladespivotally supported by said hub and said blades and pivots being soconnected that said blades are hydraulically unbalanced for movementtoward the open position of said blades at speeds above normal, andblade positioning means including a hydraulically operated servomotorhaving a cylinder and piston therein interconnected to said bla es andhydraulic pressure and return conduit means interconnected between asource of fluid pressure and said servomotor, said control system alsoincluding a control valve connected in said conduit means and operableto direct pressure against either end of said piston selectively to varythe positions of said blades and maintain them in a substantial range ofoperative positions, in combination with a hydraulic conduit connectedto opposite ends of the cylinder of said servomotor and a pressureresponsive relief valve in said conduit, said relief valve beingresponsive to pressures developed in said control system upon saidturbine exceeding a predetermined speed, whereupon said valve will opento permit passage of hydraulic fluid from the pressure end of saidcylinder functioning to prevent said movement of said blades to theopposite end thereof, thereby to permit movement of said piston andblades toward said open positions thereof and limit the speed of saidturbine to a value corresponding to that of the open position of theblades to which they have been moved by said hydraulic unbalance.

10. A hydraulic turbine including an adjustable blade runner supportedfor rotation about its axis and comprising a hub, a plurality of bladespivotally supported by said hub and said blades and pivots being soconnected that said blades are hydraulically unbalanced for movementtoward the open position of said blades at speeds .above normal, andblade positioning means intercouneeted to said blades and including acontrol valve connected by conduit means to a sump reservoir and also toa hydraulically operated servomotor controlled by said valve and havinga piston operable to vary the positions of said blades and maintain themin a substantial range of operative positions, in combination withelectrically actuated mechanism interconnected with said bladepositioning means and including a switch operable to control saidelectrical means, said switch being mounted. rc'ativc to said turbine soas to be responsive to the rotary speed or" said runner and upon saidturbine being subjected to a selected predetermined runaway speedcondition in excess of normal, said switch being operable to actuatesaid electrically actuated mechanism and cause it to actuate said valveso as to connect the pressure in the end of the servomotor serving toprevent said movement of said blades with said sump reservoir, wherebysaid blades are caused to move toward said open positions thereof andthereby limit the runaway speed of the turbine to a value correspondingto that of the open position of the blades to which they have been movedby said hydraulic unbalance.

11. The hydraulic turbine structure of claim 10 further characterized bysaid control valve having a vertically movable valve member connected bya magnetic clutch to actuating mechanism in said positioning means, saidclutch being operable by said speed responsive switch upon saidpredetermined runaway speed condition occurring, thereby to release saidvalve member for movement to a position to relieve pressure in the endof the servomotor which prevents said movement of said blades.

12. The hydraulic turbine structure of claim ll additionally including aweight connected to said valve member and operable upon release of saidclutch to shift said valve member by gravity to pressure relievingposition.

13. A hydraulic turbine including an adjustable blade runner mounted forrotation about its axis and comprising a hub, a plurality of bladespivotally supported by said hub and said blades and pivots being soconnected that said blades are hydraulically unbalanced for movementtoward the open position of said blades at speeds above normal, andpositioning means interconnected to said blades and operable to vary thepositions of said blades and maintain the same in desired normaloperating positions, said positioning means including means fracturableto disconnect said blades from said positioning means due to forcegenerated by the abnormal unbalance of said blades upon said turbineattaining a predetermined runaway speed, thereby to permit the unbalanceofsaid blades freely to move said blades toward said open positionsthereof and limit the runaway speed of saidturbine to a valuecorresponding to that of the open position of the blades to which theyhave bec moved by said hydraulic unbalance.

14. A hydraulic turbine comprising a runner having a hub and pivotallyadjustable blades thereon, the blades and pivots thereof being soconnected that said blades are hydraulically unbalanced for movementtoward the open positions of said blades at speeds above normal, each ofsaid blades having a rocker arm thereon, and positioning means includinga crosshead and fracturable means interconnecting said crosshead androcker arms on said blades, said positioning means being operablenormally to maintain said blades in desired positions of operation andalso vary the same to produce a desired turbine output at'no'r'malspeed, in combination with runaway spec limiting mechanisminterconnected with said normal positioning means and operableautomatically at speeds of a predetermined amount above normal to freethe blades from the control of said normal positioning means and permitthe said hydraulic unbalance of said blades to move the same toward saidopen positions thereof, thereby limiting the runaway speed of theturbine to a value assure corresponding to that of the open position ofthe blades to which they have been moved by said hydraulic unblance andin the event movement of one of said blades toward open position isprevented such as by foreign matter being lodged between said blade andhub of the runner said fracturable means interconnected to said bladewill be ruptured by the force exerted by the other blades upon saidcrosshead, thereby disconnecting said one blade from said crosshead andpermitting the other blades still interconnected to the crosshead tomove as directed by said inherent unbalance of the other blades to theopen position thereof.

References Cited in the file of this patent UNITED STATES PATENTS1,931,158 Biggs Oct. 17, 1933 26 Biggs Feb. 20, 1934 Biggs Mar. 13, 1934Biggs Mar. 13, 1934 Biggs June 12, 1934 Montgomery Dec. 9, 1941Rheingans May 12, 1942 Moody May 26, 1942 Seewer Aug. 14, 1945 SeewerSept. 10, 1946 FOREIGN PATENTS Switzerland Nov. 1, 1928 France Feb. 26,1929

